1. Technical Field
The invention relates to a wheel measurement system and method, and more particularly, to a wheel measurement system that uses a plurality of paths of light to measure an attribute of a wheel.
2. Background Art
A railway wheel is subject to normal wear due in large part to friction contact between the wheel and the rail. As a railway wheel wears, the profile of the running surface and many critical dimensions of the wheel change due to dynamic interaction of the wheel with the rail. Such interaction is complex and many measurements have to be made to insure the wheel complies with the appropriate safety standards for continued operation. For example, the American Association of Railroads (AAR) provides the standards for rail operation within the United States.
Thus, there is a need to accurately measure several properties of a rail wheel, including, the rim thickness, the flange thickness, the flange height, the reference groove diameter (when available), the wheel diameter and the wheel angle of attack, to ensure that the wheel operation remains safe. These safety check measurements typically take place in train yards and in train shops. Before the train can leave the yard, all the wheels are visually inspected and a wheel with noticeable wear is measured to verify that the wheel is in good condition.
Similar measurements are used in recutting (wheel truing) the wheels to restore wheel profile as wheel wear exceeds certain permissible tolerances of flange height and flange thickness. This wheel truing operation takes place in train shops. In addition, wheel measurements are used by wheel manufacturers for production quality control of railway wheels as the wheels roll off a production line. Historically, these measurements have been manually taken using specialized mechanical calipers. One such widely used mechanical wheel gauge looks like an inverted xe2x80x9cJxe2x80x9d. In use, the readings are taken and recorded by an operator directly off the mechanical gauge while the gauge is positioned against a wheel. There are several drawbacks, however, to such a mechanical gauge for the above-mentioned applications. In a situation where the wheel is installed on a train, for example, there are three major problems. First, the railway wheel has quite a few mechanical parts such as brakes, shock absorbers, axle support mechanisms and sand nozzles around it. Measurements have accordingly been difficult to take with the mechanical gauge because of the limited space around the wheel and because of the location of the flange on a railway wheel (towards the gage side of the track). Second, environmental conditions where the measurements are made are often poor. For example, dim light and limited ground clearance often makes this task extremely difficult to perform. Third, measuring a number of wheels can be laborious due to the lengthy steps required to take each measurement and the difficulty of reading the gauge.
Further, operator dependent recording of wheel measurement(s), and subsequent keypunch operations, make this important wheel wear monitoring process subject to manually induced errors. Measurement error can lead to three problems for the railroad. First, unacceptable wheels can remain in service providing an uncomfortable ride and posing a significant safety and liability hazard; second, wheels can be condemned which should be trued or reprofiled creating unnecessary expenses; and third, wheels which should be condemned are sometimes sent for truing, resulting in a disruption of the work flow in the wheel truing shop.
The mechanical gauge has been in use since 1923. Nevertheless, every year a number of train accidents are attributed to excessively worn wheels. Train maintenance staff measurement errors contribute to this safety risk. Several companies have invested heavily in computerized wheel management systems that are designed to automate the wheel maintenance process. However, the current mechanical gauge does not provide sufficiently accurate measurements to feed to such computerized wheel management systems. Furthermore, the wheel maintenance staff cannot restore a wheel to a prescribed profile when accurate wheel measurements are unavailable.
Several systems have been developed to automate the wheel measurement process. These attempts include handheld semi-automatic gaging systems and track mounted fully automatic gaging systems. Among the handheld gaging systems, one arrangement is featured in U.K. Patent Application No. GB 2183840A (granted Jun. 10, 1987 to Martti Kurkinan). This arrangement measures only rim profile using an electromechanical contact probe that travels across the rim. The measured profile is compared with a good reference profile gathered using a second probe.
Another handheld gage is described in U.S. Pat. No. 4,904,939 (granted Feb. 27, 1990 to Zahid Mian). This approach addresses the typical problems with handheld railway wheel profile measurement arrangements such as nonportability, elimination of transcription errors, and significant mechanical wear of the instrument. However, at least two difficulties remain. First, the wheel measurement process remains laborious when many wheels have to be measured quickly. Second, access to the mounted wheels remains difficult due to the presence of other mechanical parts, such as brake shoes, surrounding a mounted wheel.
Several other efforts have been made in the area of track mounted wheel measurement systems. For example, U.S. Pat. No. 3,820,016 (granted Jun. 25, 1974 to Marion Giesking) and U.S. Pat. No. 4,407,072 (granted Oct. 4, 1983 to Hoskins). Both of these arrangements utilize complicated electromechanical parts that come in contact with the wheel. Such mechanically complex arrangements present long term reliability problems, especially in outdoor environments, as well as mechanical wear and accuracy issues.
A contactless measurement method and apparatus is described in U.S. Pat. No. 4,798,963 (granted Jan. 17, 1989 to Wittkopp). This arrangement provides wheel diameter and profile measurement using multiple light sources and cameras. The apparatus employs complex mechanical operations to dispose the optical devices with respect to the wheels. The apparatus further requires extensive modifications to the rail in order to operate.
A similar arrangement is described in U.S. Pat. No. 4,798,964 (granted Jan. 17, 1989 to Schmalfuss). Based on optical measurement schemes, this arrangement uses multiple broad band light sources, a mechanical platform subject to wear, and complex optical configurations to measure wheel diameter and tread surface. Additionally, significant modifications are required to the rail for system operation. Unfortunately, this system is difficult to keep clean of dirt in the railway environment, provides questionable measurement accuracy, operates at very low speeds due to a complicated mechanical arrangement, is expensive to produce due to complex optical measuring schemes, requires significant installation space, and is not suitable for outdoor operation. A further shortcoming of this system is the critical use of a small number of data points from the tread surface of the wheel that are used to detect the wheel position and support diameter measurement. The tread surface is subject to the greatest wear and is subject to defects such as slid flats, spalling, and shelling that can cause serious errors using the measurement method described.
In another system described in U.S. Pat. No. 5,793,492 (granted Aug. 11, 1998 to Vanaki) optical devices are used to provide a series of two dimensional images of the wheel. While contactless and mechanically simple, the small number of data points used to develop some of the measurements (such as 4 points for diameter) render the system susceptible to measurement error due to wheel defects and buildup of materials such as grease and brake dust in critical measurement areas. A final shortcoming of this system is that some components of the system are as high as 2.7 inches above the top of the rail. Experience has shown that defective, worn, or broken equipment that is part of the underside of the train can come in contact with such a system and cause significant damage to precisely aligned optical components.
Other optical-based systems are described in U.S. Pat. No. 4,932,784 (granted Jun. 12, 1990 to Danneskiold-Samsoe) and U.S. Pat. No. 5,247,338 (granted Sep. 21, 1998 to Danneskiold-Samsoe et al.). These systems suffer similar shortcomings due to the small number of data points developed.
In view of the foregoing, there presently exists a genuine need for an electronic non-contact wheel measurement system capable of improving the integrity of the wheel measurement process by quickly measuring key wheel attributes irrespective of lateral and horizontal wheel movement and the size and location of isolated defects that may be present on a wheel.
The invention provides a system and method for illuminating a wheel and sensing a reflection to measure an attribute of the wheel.
A first aspect of the invention is directed to a method of measuring an attribute of a wheel having a first side and a second side, the method comprising the steps of: obtaining wheel data by: illuminating a first portion of the first side of the wheel with a first plurality of paths of light from a first light illumination device; and sensing wheel data based on a first reflection of the first plurality of paths of light from the wheel; and performing a calculation on the wheel data to measure the attribute of the wheel.
A second aspect of the invention is directed to a wheel measurement system for measuring an attribute of a wheel having a first side and a second side, the wheel measurement system comprising: a light measuring system for obtaining wheel data with light, the light measuring system including: a first light illumination device on the first side of the wheel for illuminating a first portion of the wheel with a first plurality of paths of light; and a first light sensing device for sensing a first reflection of the first plurality of paths of light from the wheel and generating the wheel data; and a control unit, in communication with the light measuring system, for measuring the attribute of the wheel from the wheel data.
A third aspect of the invention is directed to a wheel measurement system for measuring an attribute of a wheel having a first side and a second side, the wheel measurement system comprising: means for obtaining wheel data with light, the means for obtaining wheel data including: means for illuminating a first portion of the first side of the wheel with a first plurality of paths of light from a single light illumination device; and means for sensing wheel data based on a first reflection of the first plurality of paths of light from the wheel; and means for measuring an attribute of the wheel using the wheel data.
A fourth aspect of the invention is directed to a method of determining a start time for measuring an attribute of a wheel on a rail that supports the wheel with a measuring device, the method comprising the steps of: attaching a first magnetic sensor to the rail; attaching a second magnetic sensor to the rail wherein the second magnetic sensor is a known distance from the first magnetic sensor and a known distance from the measuring device; determining a first time that the wheel is detected by the first magnetic sensor; determining a second time that the wheel is detected by the second magnetic sensor; and calculating the start time for measuring using the first time, the second time and the known distance from the measuring device.
A fifth aspect of the invention is directed to a method of measuring an attribute of a wheel using a path of light, the method comprising the steps of: determining a brightness of the wheel; adjusting a brightness of a path of light based on the brightness of the wheel; illuminating a portion of the wheel with the path of light; sensing wheel data based on a reflection of the path of light from the wheel; and performing a calculation on the wheel data to measure the attribute of the wheel.
A sixth aspect of the invention is directed to a computer program product comprising a computer useable medium having computer readable program code embodied therein for measuring an attribute of a wheel, the program product comprising: program code configured to control a light illumination device for illuminating the wheel with a plurality of paths of light; program code configured to control a light sensing device that obtains wheel data based on a sensed reflection; and program code configured to perform a calculation on the wheel data to measure the attribute of the wheel.
The exemplary aspects of the present invention are designed to solve the problems herein described and other problems not discussed, which are discoverable by a skilled artisan.